Embodiments described herein relate generally to devices for use in radiation therapy and more particularly to a head restraint system for radiation, e.g., proton, therapy.
Patient immobilization is essential for the safety and efficacy of radiation, and particularly, proton, therapy. In particular, patients undergoing proton therapy are typically disposed on a treatment table or couch associated with the proton particle accelerator instrument. Various couch-tops and overlays or other patient support panels are commercially available for disposition on the treatment table, with the patient being disposed on the couch-top/overlay. Fixation or immobilization devices are available for use with the couch-tops/overlays to position the patient in the same anatomic position and location on the treatment table as on the planning table (i.e., the table upon which the radiation treatment plan was established).
One type of immobilizing and positioning device used for treating the head and neck region is the thermoplastic mask. This device is a perforated mask formed of a thermoplastic material or web that is heated and stretched over the head and neck areas (and sometimes portions of the upper torso) while the patient is disposed on the overlay on the planning table, with peripheral portions of the mask being connected to the overlay by clips or other attachment means forming a portion of the mask until the thermoplastic cools and sets. That action results in a mask that is molded to closely conform to the patient's individual anatomy to provide a very secure fit to immobilize the patient's head at a precise desired position for subsequent radiation treatment. Those same clips or other attachment means are then used to releasably secure the mask to respective connectors, brackets or some other means on the overlay or patient support panel on the treatment table when the patient is to be given the radiation treatment to immobilize the patient's head at the position and orientation that was established when the mask was molded.
For proton therapy, it is important that the patient's head be rigidly supported and immobilized in the desired position, while ensuring that the mask is as comfortable as possible. As is known, the thermoplastic material of the mask may tend to shrink somewhat after its initial molding. As a result, when the mask is applied to patient doing the subsequent radiation treatment the fit may not be exactly as initially taken so that the patient's head is not immobilized at the precise position desired and comfort is compromised. Thus, a need exists for a system to ensure that the mask can be adjusted to hold the patient's head at the precise position as when the mask was molded on the patient. The subject invention addresses that need by providing a head restraint system which is adjustable to ensure that the patient's head (and, if desired, head and upper torso) can be repeatedly and comfortably immobilized at a desired position by a thermoplastic mask connected to the patient support panel or overlay on which the patient is disposed.